1. Field of the Invention
The present invention relates to a backlight unit for, for example, liquid crystal display (LCD) devices as typified by a liquid crystal television, and more particularly, to a technology for improving color purity of emission colors of a backlight unit.
2. Description of the Related Art
Generally, fluorescent tubes using R (red), G (green), and B (black) as primary colors are used for a backlight unit for LCD devices as typified by a liquid crystal television. Such fluorescent tubes have a feature that the emission intensity of red wavelength light is lower in comparison with those of green and blue, and therefore, the color purity of emission colors of backlight unit is not sufficient, thereby causing a problem of affecting the color reproducibility of a display image in a LCD device. In particular, pure red is hard to be displayed in a LCD device.
Here, in a patent literature 1 (Unexamined Japanese Patent Publication No. 2004-139876), a LCD device intended to improve the color reproducibility of a display image by using two kinds of light sources: a fluorescent tube and a LED (light emitting diode), in a backlight unit is disclosed. A LCD device C configured as described above is illustrated in FIG. 7 (quoted from FIG. 7 in Patent literature 1). FIG. 7(a) shows an elevation view of a conventional LCD device C, and FIG. 7(b) shows a sectional side view of a conventional LCD device C.
As illustrated in FIG. 7, LCD device C comprises: a plurality of fluorescent tubes 31 arrayed in up and down directions, a LED 32 for emitting a red wavelength light arrayed in between each of Fluorescent tubes 31, an inverter circuit 33 for controlling a drive of Fluorescent tube 31, a LED lighting circuit 34 for controlling a light emission of LED 32, a dimming control means 35 for adjusting the emission intensity of Fluorescent tube 31 and LED 32, a power supply circuit 36, a reflection sheet 37A as a optical member of every kind, a diffusion plate 37C, a diffusion sheet 37D, a prism sheet 37E, a reflection polarizing sheet 37F, a chassis 38 for housing those aforementioned, and a LCD panel 39 for displaying an image.
In LCD device C configured as mentioned above, improvement of color reproducibility of a display image is provided since the emission intensity of R (red) wavelength light by Fluorescent tube 31 is compensated by the light emission of red wavelength light by LED 32 arrayed in between each of Fluorescent tubes 31, thereby improving color purity.
However, in LCD device C, the emission intensity of red wavelength light of Fluorescent tube 31 in the outside of Fluorescent tubes 31 arrayed in upper and lower ends of LCD device C cannot be compensated since LED 32 is arrayed only in between each of Fluorescent tubes 31. Therefore, in LCD device C, the emission colors of a backlight are different between near the upper and lower ends and near the center, and thus causing a problem of color shading generated in a display image in LCD device C.
Consequently, this invention has been invented considering the foregoing conditions, and the purpose of this invention is to provide a backlight unit capable of improving color purity of a prescribed emission color as well as obtaining an uniform emission colors in the entire device, and a LCD device comprising thereof.